There are literally millions of tons of coal in the United States alone that are found in thin coal seams (having a thickness of about four feet or less), and ultra thin coal seams (having a thickness of around two feet or less). Utilizing conventional equipment and techniques the vast majority of this coal is unrecoverable. While auger miners can be successful in thin and ultra thin seams, augers are very limited in the depth of bore they can form (typically limited to about 150 feet), and because of the circular bores that they form leave a great deal of coal between penetrations. It was for that reason that the continuous mining machine in U.S. Pat. No. 3,874,735 (the disclosure of which is hereby incorporated by reference herein) was developed. That mining machine, marketed in commercial form by Lee-Norse under the trade designations CM245 and CM285, is the shortest continuous miner (non-auger) believed to ever have been commercialized. For example the CM245 has a chassis height of only about 24 inches, and can be used in coal seams as thin as 30 inches. While that machine is a significant advance in the art and has great functionality for a number of thin coal seams, its design makes it--as a practical matter--impossible to reduce its size further to allow it to be used in ultra thin coal seams.
According to the present invention a continuous mining machine is provided which uses the same basic concepts of the CM245 and 285, such as shown in U.S. Pat. No. 3,874,735, but makes a few changes to the construction that allows it to be made even shorter, so that is can effectively mine coal seams having a thickness of about 24 inches or less. The continuous mining machine according to the invention has a chassis height of only about 19 or 20 inches, and a maximum cutter diameter of about 22 inches (preferably 21 inches), yet it can effectively mine coal in seams. The mining machine according to the invention is also preferably controlled utilizing color cameras which scan at least the ceiling and the floor of a bore being formed to ensure that coal is primarily being cut rather than surrounding rock. Also according to the present invention a continuous mining machine can be utilized in an unusual technique for recovering as much coal as possible from a single complete penetration by forming angled bores into the side walls of the main bore as the mining machine is being withdrawn. Utilizing the mining machine according to the invention rather than being restricted to a bore length of about 150 feet, such as is conventional with augers, bores from 300 to 600 feet may be constructed, with additional coal recovered during withdrawal.
According to one aspect of the present invention a continuous mining machine is provided comprising the following components: A chassis supported by crawler tracks, and having a front and a rear and elongated in a first dimension between the front and the rear. A substantially horizontal axis powered cutter head mounted to the front of the chassis. A conveyor mounted to the chassis and including an endless conveyor chain. The chain connected to first and second sprockets, the first sprocket mounted for rotation about a first shaft adjacent the rear of the chassis, and the second sprocket mounted for rotation about a second shaft adjacent the front of the chassis but between the first sprocket and the cutter head. The first; and second shafts rotatable about axes generally perpendicular to the first dimension. And, at least one motor mounted adjacent the rear of the chassis for driving the first shaft to thereby drive the first sprocket and the conveyor.
The second shaft preferably comprises an idler shaft, and the machine further preferably includes a gathering head mounted adjacent the front of the chassis and below the cutter head and at least partly to the rear of the cutter head, for gathering material cut by the cutter head and moving the cut material to the conveyor. The gathering head preferably comprises a pair of counter-rotating discs with upstanding vanes, and an angled deck substantially coplanar with the discs; and wherein the second shaft has first and second transmission elements connected thereto, the first and second transmission elements operatively connected to the discs for effecting counter-rotation driving thereof. The angled deck, during normal operation, makes a maximum angle of about 10.degree. with respect to the dimension of elongation of the chassis. The chassis has a maximum height of about 20 inches (e.g. a height of about 19 inches) and the cutter head has a maximum effective diameter of about 22 inches (e.g. about 21 inches), as further explained below. The second sprocket has a maximum diameter of about eight inches and is mounted beneath the deck, and preferably includes four tapered teeth. A plurality of cross bars are preferably connected to the chain for moving conveyed material (typically coal) from the gathering heads to the rear of the chassis.
The cutter head drive is also preferably specially constructed so that it is assured that a minimum height can be achieved. For example the drive sprocket or sprockets (typically two are provided adjacent opposite ends of a shaft) preferably comprises a five tooth sprocket having a maximum diameter of about 7.5 inches (e. g. about 7.02 inches) on about a four inch diameter shaft, with the cutting head effective diameter (the trace of the cutting chain bits) at that area of about 16 inches or less (e. g. about 15.3 inches). The driven sprocket at the front of the head, where the actual cutting is done, may comprise a ten tooth sprocket with a maximum diameter of about 14 inches (e. g. about 13.35 inches), and with the cutting head effective diameter a maximum of about twenty two inches (e. g. about 21.04 inches). The cutting chain may comprise a conventional cutting chain having alternating connector and cutting bit links, e. g. Number 73473 clearance chain available from The Cincinnati Mine Machinery Co. of Cincinnati, Ohio.
The mining machine further comprises a first color video camera mounted on the chassis or the cutter head in a position to scan material being cut above the cutter head and utilizable to determine the color thereof, the first video camera connected to a monitor to the rear of the chassis. The mining machine forms a floor during operation, and preferably further comprises a second color video camera mounted to the chassis or the cutter head in a position to scan the floor cut by the mining machine and utilizable to determine the color thereof, the second video camera connected to the monitor.
The second shaft typically has first and second transmission elements (preferably gears) connected thereto, the first and second transmission elements operatively connected (through other gears in the preferred embodiment) to the discs for effecting counter rotation driving thereof.
According to another aspect of the present invention a continuous mining machine is provided comprising the following components: A chassis supported by crawler tracks, and having a front and a rear and elongated in a first dimension between the front and the rear. A powered cutter head mounted to the front of the chassis. A conveyor mounted to the chassis and including an endless conveyor chain. The chain connected to first and second sprockets, the first sprocket mounted for rotation about a first shaft adjacent the rear of the chassis, and the second sprocket mounted for rotation about a second shaft adjacent the front of the chassis but between the first sprocket and the cutter head. The first and second shafts rotatable about axes generally perpendicular to the first dimension. At least one motor for driving one of the first and second shafts to thereby drive one of the sprockets and the conveyor. A gathering head mounted adjacent the front of the chassis and below the cutter head and at least partly to the rear of the cutter head, for gathering material cut by the cutter head and moving the cut material to the conveyor, the gathering head comprises a pair of counter-rotating discs with upstanding vanes, and an angled deck substantially coplanar with the disc. The second shaft having first and second transmission elements connected thereto, the first and second transmission elements operatively connected to the discs for effecting counter-rotation driving thereof. The angled deck during normal operation making a maximum angle of about 10.degree. with respect to the dimension of elongation of the chassis. And, the chassis having a maximum height of about twenty inches, and the cutter head having a maximum diameter of about twenty two inches. The second sprocket has a maximum diameter of about eight inches and is mounted beneath the deck.
The invention also relates to a method of mining coal in thin seams. The mining machine described above is particularly suited for practicing the method of the invention, although other mining machines also may be utilized. According to the method of the present invention seams having an average thickness of less than four feet may be mined utilizing a continuous mining machine having a chassis mounted by crawler tracks, a cutter head at the front of the chassis, an articulated rear end, a first conveyor for conveying cut coal from the cutter head to the rear of the chassis, and a second conveyor operatively associated with the rear end to convey coal from a bore toward a mouth of the bore, the continuous miner having a predetermined length from the cutter head to the rear of the chassis. The method preferably comprises the steps of: (a) Forming a main mine bore, having first and second side walls, a roof, and a floor, by powering the crawler tracks and cutter head to move the continuous miner through the mine mouth into the coal seam a depth of more than 150 feet in a first direction, while cutting coal and conveying the coal toward the mouth using the first and second conveyors. (b) After the practice of step (a), retracting the continuous miner a distance of greater than about ten feet. And, (c) after the practice of step (b), forming a secondary mine bore by powering the crawler tracks and the cutter head to move the continuous miner into the coal seam through the main mine bore side walls at an angle of greater than about 20.degree. and less than about 80.degree. (e.g. between about 30.degree.-50.degree.) to the first direction for a distance roughly equal to the predetermined length of the miner (e.g. between about 20-40 feet), while cutting coal and conveying cut coal toward the mouth using the first and second conveyors.
The method also preferably comprises the further step (d) of repeating steps (b) and (c) at least once during the practice thereof. Step (c) is typically practiced by moving the mining machine into contact with the first side wall of the main bore, and step (d) is practiced after (c) by moving the miner into contact with the second wall of the main bore. Step (d) is also practiced a plurality of times, alternating between moving the miner into contact with the first side wall and the second side wall of the main bore. The method may be practiced in coal seams having an average thickness of about three feet or less, and even in ultra thin coal seams having an average thickness of about two feet or less.
Preferably during the practice of step (a) the miner is remotely controlled by a human operator, and the miner has at least a first color video camera mounted thereon; and the method preferably comprises the further step (d) of scanning the roof of the bore adjacent the cutter head to determine the color thereof, and then the human operator adjusting, if necessary, the position of the cutter head and the vertical orientation of the miner in response to that scanning. The miner typically also has a second color video camera mounted thereon, and there is the further step (e) of scanning the floor of the bore with the second video camera to determine the color thereof, and then the human operator adjusting, if necessary, the position of the cutter head and the vertical orientation of the miner in response to that scanning.
Step (a) is typically practiced to penetrate the coal seam a distance of over 150 feet, typically between about 300-600 feet. The mining machine utilized in the practice of the method of the invention typically has a length of about 25 to 30 feet (e.g. about 28 feet), and in any event steps (c) and (d) are typically practiced to penetrate the coal seam a distance of between about 20-40 feet in forming each secondary bore.
It is the primary object of the present invention to provide a continuous miner, and mining method, that can mine ultra low thickness coal seams to a depth of more than 150 feet without putting a human operator at risk. This and other objects of the invention will become clear from an inspection of the detailed description of the invention and from the appended claims.